For best results, see LASORS, but if you have an ICAO ATP with over 1000 hours and a multi-crew type rating, you are exempt formal training (just tick the box on the application form) but must take all the exams
. Since your ATP is a CAA one, you likely won't have done Human Factors anyway.
PM me if you have any further queries - you will definitely need some exam prep, and
ATPL QUESTION TEST QCM Theorical JAA ATPL and CPL is a free database
cheers
phil